Semiconductor devices have been increasingly integrated to satisfy high performance characteristics and low manufacture costs which are desired by customers. Since integration of the semiconductor devices is an important factor in determining product price, high integration is increasingly demanded in particular. Integration of typical two-dimensional or planar semiconductor memory devices is determined in part by the area occupied by a unit memory cell, such that it is greatly influenced by the level of technology for forming fine patterns. However, increasingly expensive processing equipment that is needed to increase pattern fineness may set a practical limitation on increasing the integration of the two-dimensional or planar semiconductor memory devices. Therefore, there have been proposed three-dimensional semiconductor memory devices having three-dimensionally arranged memory cells.